I'm Losing Power in 5th....Any Idea's?
 

I'm running stock bore/stroke 16:1 piston, A1/A2 cams, 1mm over intake/exhaust valves, porting, TM45 w/RW alky kit, Vortec CDI, 4-Snow tires, fresh spark plug gapped .022, 15 tooth counter sprocket and my DS is nose dives in 5th gear around 6200-6300 rpm. It feels like it's running out of fuel. 1st through 4th it pulls fine. If I leave it in 4th on extended runs it's fine but the minute I shift into 5th and rpms get up to around 6300 then rpm's start to drop...no back firing or blubbering. I jetted way up and way down trying to solve the problem with no avail. We then drilled a hole in the gas cap for better venting. The petcock has been drilled out and filters removed to allow more flow. I bent the tab slightly on the floats to allow more fuel in the bowl...rpm's still dropped. Even with the largest main jet (330) in the RW alky kit the plug looks a tad on the lean side. Everything points to fuel starvation but I know of several larger bore/stroke motors running the same set up not acting like this. I then started messing with the Vortec timing curves. I usually run in #1 position which is very close to RW cdi curve and it ran fine...previously. I then switch to the #3 curve and made a couple of passes and 5th pulled fine. I then switch back to the #1 position and 5th pulled fine but a couple of passes later, rpm's started to drop in 5th again. Now it's starting to look like I've got a bad cdi or not enough current to fire the alky under a load in 5th. I tried rolling the throttle on while short shifting 1st-4th and it pulled. I cruised 30 mph for a short distance in 5th then held it wide open and it pulled until 6300 then rpm's fell. Is there anyway of testing the Vortec CDI and if so what number should I be looking for?

Thanks
JMiller

I'm Losing Power in 5th....Any Idea's?
 

Will it pull past 6300 in all the other gears?. I know when I installed the vortex on my buddies 03 baja, I had to fix the switch on the handlebars, it was not working at all, and would only let it pull to 6000 or so. The switch was not making contact inside, once I fixed that it was ok. If it is pulling past 6000 in all gears except fifth then It looks like a fuel problem. Try pulling the jets out all together and see if it gets any better. But I would check the switch on the cdi. Let us know.

I'm Losing Power in 5th....Any Idea's?
 

Maybe you need a fuel pump..? I know that allot of +550cc banshees pretty much have to run a pump on methanol

I'm Losing Power in 5th....Any Idea's?
 

It will rev out 1-4 gears with no problems in #1 curve and using the #3 curve will pull 5th. After I make a few passes using the #3 curve then switch back to the #1 curve, it will pull 5th a pass or two then rpm's start to drop again. I'm not ruling out fuel starvation but when I was cruising a steady 40 mph or so in 5th gear I pulled in the clutch and let off the gas to allow the fuel bowl fill up then took off full throttle still in 5th and once again rpm's dropped when it reached 6300. I also did this when I was on full throttle...I nailed it 1-4 then pulled in the clutch and let off the gas for a couple of seconds then shifted into 5th and got back on the throttle...rpm's dropped soon thereafter. I think my cdi box is crapping out on me. That little rubber cap over the curve adjustment dial on the box fell off....do you think water is getting in there causing problems? The only real way to find out is put another cdi back on. I could put my stocker back on. Hmmm.

JMiller

I'm Losing Power in 5th....Any Idea's?
 

this is just out of the blue but could it be a gas cap vent prob? do you have a vented gas cap? if not check the vent line make sure its not kinked or bent. Just a thought.
Sam

Sorry my bad, I just read a little closer, you all ready tried this.

I'm Losing Power in 5th....Any Idea's?
 

Check all vents and drilled gas cap for vent yesterday...problem still exsists.

JMiller

I'm Losing Power in 5th....Any Idea's?
 

Make double sure you didnt break a cam. It is hard to notice a broken cam until you get into the taller gears. you should be able to take your carb AND exhaust off and watch the valves work while turning over the motor.




bigger.

I'm Losing Power in 5th....Any Idea's?
 

The cam broke right in half! No damage at all but only the lobe closest to the sprocket was working. The bike would still take off great but in the upper gears it would FADE badly. We also thought it was a fuel problem.


bigger.

I'm Losing Power in 5th....Any Idea's?
 

I've run the woods CDI and the vortex CDI without spark problems under high boost. I set the gap at 0.018" and use D10EA plugs.

Sounds like a fuel starvation problem.

I think Mr HP said dual carbs were a good idea for alcohol to get the fuel flow needed.

You should be running very rich, like 4:1 or 4.5:1 at full throttle to make max power. To do this you need to flow a ton of fuel!

You might try taking out the main jet.

EGT and O2 sensors help too.

I'm Losing Power in 5th....Any Idea's?
 

Who makes the best fuel pump set up for a DS? I know that Predators use a pulse pump...would this work or would I be better off using a electric pump? I was looking at Facet electric pump (12 volt/1amp) that produce 1.5-4.5 psi. If I go with a electric pump should I get a higher psi then regulate it? If I went with a pulse pump where do you get the vacume to run it? June 11th I'm making a trip to MrHP's dyno and want to have potential fuel delivery problems out of the way so that we can concentrate on jetting.

Sometime back I read where a guy ran a longer fuel line making a couple of loops above the carb and below the petcock and claimed to rid his starvation problems. Any of you guys hear of this? I tried it on my alky 465 with a 14:1 piston and I could run 1/8th mile wide open with no problems on a FCR41. Perhaps I should give it a try...huh?

I will try taking mj out and gapping plugs to .018

I'll get to the bottom of this yet. It's got to be a simple fix.

Thanks for all your input!
JMiller